67 Mustang Wiring For Fog Lights (Oct 21, 2018) &horbar; Knowledge about 67 mustang wiring for fog lights has been published by Maria Rodriquez and tagged in this category. Sometimes, we might have to slightly modify the design, colour, or even accessories. We require a whole new thought for it then one of these is this 67 mustang wiring for fog lights.. In the engine compartment fuse box, check the 20A DRL, FOG, HORNS FUSE and confirm that the FOG LAMPS RELAY is in place. Fog lamp operation depends upon the DRL setting so the DRL circuit may be defective which would account for the headlight problems.. The fog light feed starts on the passenger side with a blue 2-plug which exits next to all the other light plugs below the radiator. 1 side has a grey wire (+) and the other side is black (-). The black wire junctions into a ground "joint" about 6 inches into the harness..